The effect of adsorption on the measurement of diffusion coefficients by the Taylor dispersion technique is investigated by modifying the governing equation to account for reversible, nonequilibrium adsorption. The resulting two-dimensional equations are solved by an explicit finite-difference technique. Experimental data for the acridine-carbon dioxide system indicated that acridine adsorbs on the walls on the tubing and these data were investigated with this model. The influence of various parameters including the number of sites and the rates of adsorption/desorption was investigated by conducting a parametric sensitivity analysis on the model. It was found that adsorption of the solute on the wall of the tubing could produce an error as high as 35% on the measured diffusion coefficient compared to the actual diffusion coefficient. Examination of the influence of each of the parameters will enable future investigators to reduce the effect of adsorption in the measurement of diffusion coefficients by Taylor dispersion. © 1996 Plenum Publishing Corporation.